1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 // Implementation of AudioInputStream for Mac OS X using the special AUHAL
6 // input Audio Unit present in OS 10.4 and later.
7 // The AUHAL input Audio Unit is for low-latency audio I/O.
9 // Overview of operation:
11 // - An object of AUAudioInputStream is created by the AudioManager
12 // factory: audio_man->MakeAudioInputStream().
13 // - Next some thread will call Open(), at that point the underlying
14 // AUHAL output Audio Unit is created and configured.
15 // - Then some thread will call Start(sink).
16 // Then the Audio Unit is started which creates its own thread which
17 // periodically will provide the sink with more data as buffers are being
19 // - At some point some thread will call Stop(), which we handle by directly
20 // stopping the AUHAL output Audio Unit.
21 // - The same thread that called stop will call Close() where we cleanup
22 // and notify the audio manager, which likely will destroy this object.
24 // Implementation notes:
26 // - It is recommended to first acquire the native sample rate of the default
27 // input device and then use the same rate when creating this object.
28 // Use AUAudioInputStream::HardwareSampleRate() to retrieve the sample rate.
29 // - Calling Close() also leads to self destruction.
30 // - The latency consists of two parts:
31 // 1) Hardware latency, which includes Audio Unit latency, audio device
33 // 2) The delay between the actual recording instant and the time when the
34 // data packet is provided as a callback.
36 #ifndef MEDIA_AUDIO_MAC_AUDIO_LOW_LATENCY_INPUT_MAC_H_
37 #define MEDIA_AUDIO_MAC_AUDIO_LOW_LATENCY_INPUT_MAC_H_
39 #include <AudioUnit/AudioUnit.h>
40 #include <CoreAudio/CoreAudio.h>
42 #include "base/cancelable_callback.h"
43 #include "base/memory/scoped_ptr.h"
44 #include "base/synchronization/lock.h"
45 #include "media/audio/agc_audio_stream.h"
46 #include "media/audio/audio_io.h"
47 #include "media/audio/audio_parameters.h"
48 #include "media/base/audio_block_fifo.h"
53 class AudioManagerMac;
56 class AUAudioInputStream : public AgcAudioStream<AudioInputStream> {
58 // The ctor takes all the usual parameters, plus |manager| which is the
59 // the audio manager who is creating this object.
60 AUAudioInputStream(AudioManagerMac* manager,
61 const AudioParameters& input_params,
62 AudioDeviceID audio_device_id);
63 // The dtor is typically called by the AudioManager only and it is usually
64 // triggered by calling AudioInputStream::Close().
65 virtual ~AUAudioInputStream();
67 // Implementation of AudioInputStream.
68 virtual bool Open() OVERRIDE;
69 virtual void Start(AudioInputCallback* callback) OVERRIDE;
70 virtual void Stop() OVERRIDE;
71 virtual void Close() OVERRIDE;
72 virtual double GetMaxVolume() OVERRIDE;
73 virtual void SetVolume(double volume) OVERRIDE;
74 virtual double GetVolume() OVERRIDE;
76 // Returns the current hardware sample rate for the default input device.
77 MEDIA_EXPORT static int HardwareSampleRate();
79 bool started() const { return started_; }
80 AudioUnit audio_unit() { return audio_unit_; }
81 AudioBufferList* audio_buffer_list() { return &audio_buffer_list_; }
84 // AudioOutputUnit callback.
85 static OSStatus InputProc(void* user_data,
86 AudioUnitRenderActionFlags* flags,
87 const AudioTimeStamp* time_stamp,
89 UInt32 number_of_frames,
90 AudioBufferList* io_data);
92 // Pushes recorded data to consumer of the input audio stream.
93 OSStatus Provide(UInt32 number_of_frames, AudioBufferList* io_data,
94 const AudioTimeStamp* time_stamp);
96 // Gets the fixed capture hardware latency and store it during initialization.
97 // Returns 0 if not available.
98 double GetHardwareLatency();
100 // Gets the current capture delay value.
101 double GetCaptureLatency(const AudioTimeStamp* input_time_stamp);
103 // Gets the number of channels for a stream of audio data.
104 int GetNumberOfChannelsFromStream();
106 // Issues the OnError() callback to the |sink_|.
107 void HandleError(OSStatus err);
109 // Helper function to check if the volume control is avialable on specific
111 bool IsVolumeSettableOnChannel(int channel);
113 // Our creator, the audio manager needs to be notified when we close.
114 AudioManagerMac* manager_;
116 // Contains the desired number of audio frames in each callback.
117 const size_t number_of_frames_;
119 // Pointer to the object that will receive the recorded audio samples.
120 AudioInputCallback* sink_;
122 // Structure that holds the desired output format of the stream.
123 // Note that, this format can differ from the device(=input) format.
124 AudioStreamBasicDescription format_;
126 // The special Audio Unit called AUHAL, which allows us to pass audio data
127 // directly from a microphone, through the HAL, and to our application.
128 // The AUHAL also enables selection of non default devices.
129 AudioUnit audio_unit_;
131 // The UID refers to the current input audio device.
132 AudioDeviceID input_device_id_;
134 // Provides a mechanism for encapsulating one or more buffers of audio data.
135 AudioBufferList audio_buffer_list_;
137 // Temporary storage for recorded data. The InputProc() renders into this
138 // array as soon as a frame of the desired buffer size has been recorded.
139 scoped_ptr<uint8[]> audio_data_buffer_;
141 // True after successfull Start(), false after successful Stop().
144 // Fixed capture hardware latency in frames.
145 double hardware_latency_frames_;
147 // The number of channels in each frame of audio data, which is used
148 // when querying the volume of each channel.
149 int number_of_channels_in_frame_;
151 // FIFO used to accumulates recorded data.
152 media::AudioBlockFifo fifo_;
154 // Used to defer Start() to workaround http://crbug.com/160920.
155 base::CancelableClosure deferred_start_cb_;
157 DISALLOW_COPY_AND_ASSIGN(AUAudioInputStream);
162 #endif // MEDIA_AUDIO_MAC_AUDIO_LOW_LATENCY_INPUT_MAC_H_